The invention relates to a chair having a seat and a back whose inclination can be adjusted.
In a prior art chair of this type (European Pat. No. 0,185,388), corresponding to U.S. Pat. No. 4,685,730 change of a chair from the working position to a reclining position causes an adjustment device to effect a simultaneous, synchronous displacement of a front seat portion (reference numeral 2 thereof) as well as a backrest and a pelvis-hip support, the initial section of which extends at least over the entire hip region of the chair user's spine. If the prior art chair is in the working position, the seat surface extends approximately horizontally. The adjustment device includes an adjustment lever which is curved about approximately 90.degree. and is articulated to the seat support and engages in an articulated manner at the backrest. The adjustment lever is pivotable by means of a pneumatic cylinder. The pelvis-hip support is supported on the adjustment lever by way of an approximately vertically disposed spring "ressort mecanique" (page 3, paragraph 5).
It is also known to divide the chair contour supporting the chair user into a section forming the seat surface, a pelvis supporting section and a section forming the backrest and to make the pelvis support adjustable. The latter may also be done in such a manner that the user has no influence on the adjustment (German Pat. No. 1,256,840, column 3, lines 39-47).
In a prior art chair of a comparable type, the rocker can be fixed in a set position by means of a friction locking multiple disc clutch through which passes a clamping rod, and a positive and synchronous adjustment of the inclination of the seat section and the backrest is provided approximately in a ratio of 1:2 (Embodiment of FIGS. 6, 6a), for example see U.S. Pat. No. 4,693,514 and Canadian Application No. 486,589.